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Computed fully nonlinear wave pattern behind a Series 60, CB = 0.6 model at a Froude number of 0.3 (computation details given in Scorpio et al., 1996). |
Many of the critical aspects of marine design are associated with hydrodynamic characteristics such as current and wave loads, resistance, propulsion, maneuvering, and seakeeping.
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Computed fully nonlinear wave pattern behind a Series 60, CB = 0.6 model at a Froude number of 0.3 (computation details given in Scorpio et al., 1996). |
The department continues to have a strong research program in these areas. This theoretical and numerical work is a direct complement to the experimental research carried out in the Marine Hydrodynamics and Ocean Engineering Laboratories. Many research projects have both experimental and analytic components.
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Impact Hydrodynamics: comparisons between experimental impact coefficients and theory for a flared body (Wang and Troesch, 1996). |
Most of the analytic research in recent years has involved numerical marine hydrodynamics using computational methods to predict the hydrodynamic behavior of a marine vehicle or offshore structure. Recent projects have included the following:
Fully Nonlinear Water-Wave Computations. A boundary element method has been developed to solve water-wave problems using the fully nonlinear free surface boundary conditions rather than the traditional linearized form. The problem is solved in the time domain using a desingularized technique at each time step. The nonlinear computations have been used to study such phenomena as wave-wave interactions, wave run-up on offshore platforms, the effects of above-water hull shape, and large amplitude motions.
Turbulence Modeling for the Reynold's Averaged Navier-Stokes Equations (RANS). Traditional turbulence models for RANS code computations are not valid near the free surface. Experimental and numerical investigations are being conducted to develop improved turbulence models for free surface flows.
Planing Boat Hydrodynamics. Planing boat hydrodynamics is unique in that the high speed generates a spray sheet and attendant spray root line. New numerical models are being developed to compute this behavior in order to accurately predict planing boat performance in calm water and waves. Impact pressures and loads result from the slamming that can occur on the fore-bottom and bow flare of monohulls, the underside of the cross-deck for multihulls, and the lower deck of large off-shore structures in extreme waves. The design of the structure in these areas requires a detailed knowledge of the distribution and duration of the slamming pressure. Three-dimensional impact calculations are especially difficult because of the complex nature of the flow in the impact region.
Modeling of Nonlinear Shallow Water Motions. The prediction of the current velocities in the nearshore region is of practical importance since it is these currents that displace sediment during storm conditions and cause coastal erosion. These currents are also thought to be responsible for the recovery of beach sand during calmer wave conditions. The physics underlying the generation of nearshore currents and their effects on the coastal morphology is still poorly understood. We are developing and utilizing numerical models to simulate currents in the nearshore region given the bathymetry of the area of interest and the offshore wave conditions. The predicted current field is then used to understand the coupling between the hydrodynamics in the nearshore zone and changes in the coastal morphology.
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Computer vorticity field in the nearshore region. The beach is located to the left of the panel and the coordinates x and y point offshore and alongshore, respectively. The wave-induced longshore current, which flows from the bottom to the top of the panel, and the associated vortex pairs seen here are partly responsible for sediment transport in the coastal zone. (Özkan-Haller and Kirby, 1999) |
FACULTY: Beck, Perlin, Sirviente, Troesch, Walker